Hold on a sec - leap seconds granted a last-minute reprieve

A decision to kill leap seconds and permanently change how time is measured has been deferred until 2015 by the International Telecommunication Union.

A meeting of ITU Radiocommunication Assembly reps on Thursday was unable to reach a decision on whether to stop adding leap seconds to Coordinated Universal Time (UTC) to keep it in check with our world's uneven rotation.

The ITU will now spend the next three years conducting further studies "to ensure that all the technical options have been fully addressed" and to hold further discussions with members.

In a statement, the ITU said its Secretary-General, Hamadoun Touré, considered the move to postpone the decision would "ensure that all stakeholders have been adequately associated with a step which will clearly influence our future".

Leap seconds were introduced in 1971 to keep UTC accurate: UTC is measured using the rotation of the Earth and super-accurate International Atomic Time (TAI).

The problem is that the Earth's spin is not constant - it's slowing down - while TAI is a constant. Leap seconds are added every so often to keep the gap between the atomic clocks and the time according to the planet's rotation at less than 0.9 seconds.

Supporters of the change argue leap seconds are unworkable in the long-term and are an unnecessary and potentially dangerous addition for systems relying on precise time measurements, for example, to pin-point their location. Their opponents claim there's a lack of credible evidence to suggest that serious problems are caused by leap seconds and further counter that computers can easily cope with delaying time for a brief moment.

Decoupling UTC from the rotation of the Earth would bring to an end a millennia of telling time using the spin of the Earth as it orbits the Sun.

The ITU's leadership appears to favour the change as it would eliminate need for what it called "specialized ad-hoc time systems". It added, however: "[This] may have social and legal consequences when the accumulated difference between UT1 - Earth rotation time - would reach a perceivable level - two to three minutes in 2100 and about 30 minutes in 2700." ®